Saturday, October 16, 2010

New Project - 2304 MHz Transverter - Tuning the Front End

OK, I got the ambition to hook it all up today and start tuning the receiver. I used a very crude setup. The only signal source I have that will generate a signal near 2304 MHz is the second harmonic of the local oscillator in my 1296 transverter. I used that as the signal source.

I had to set up the signal source about 20 feet away from the workbench to keep the RF from being picked up directly on the 13 cm circuit board. I put a homebrew 1/4 wavelength antenna on the input side of a 0 - 50 dB attenuator, then fed the other side of the attenuator into the RF in on the converter. I used my FT-817 as the IF. Tuned to USB, I easily spotted the signal very close to 144 MHz on the IF. The signal was about an S-2 with 0 dB of attenuation inline with the little 3 cm long antenna. I began snowflaking the hairpins, adding small strips of copper to the hairpins where I saw an increase in signal and soldered them in place. There were a couple places that gave huge increases in gain, in the middle of the filter. After about 2 hours work, I was able to get the signal up to about an S-7 with 20 dB of attenuation in line with the little whip antenna I was using as a pickup.

The frequency stability appeared to be quite good, there was some drift when I first powered it all up, but that quickly settled down after it was on for about 5 minutes or so. I did not have to touch the VFO dial in the IF rig after that time.

The next step will be in building the transmit side of the transverter. I am still waiting on my order to come in from Down East- one of W1GHZ's power meters and a couple of MMIC low level amplifier boards. I need the power meter in order to tune the TX filter which I have yet to build.

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About Me

Ham radio: I am an Extra Class Amateur Radio operator, licensed in 1980. I tend to be more of an experimenter rather than "operator". Currently into SDR and microwave radio mostly.
Astronomy: I'm getting back into astronomy after being away from the hobby for about 30 years. I consider myself a newcomer, because a lot has changed since I was into it before. Currently all I'm using is a 70 mm refractor and a common, everyday webcam for photography of the planets. I also have a Pentax K-1000 that I may end up doing some simple night sky photography.